There's a reason most consumer cameras are no more than 13 megapixels. There's no point for a regular consumer to need more. At 13 megapixels you can blow up the picture to poster size without much trouble. The tech is available to make much higher MP cameras but the only benefit to that for 99.5% of people would be digitally zooming and it's not worth what it would cost to put it in the camera.
Image quality is completely different from image detail.
Also I should point out something that no one else has mentioned (that I've seen anyway).... a 5mp camera can store a lot more pictures in 16gb of memory than an 8mp camera.